It is often necessary in orthopedic surgery to affix a metal device into the patient's bone. Typically, surgery such as bone fracture repair uses bone screws to attach metal plates to the bone in order to restrict movement and to ensure the correct positioning of the bones being repaired. However, in other scenarios, the metal device is intended to permanently be incorporated into the patient's skeleton. A common situation is hip or knee joint replacement where the implant is intended to durably adhere to the patient's bones.
Some clinical scenarios, such as patients who have had multiple revision surgeries or bone tumor resections are challenging for current devices, in particular when there is a short segment of bone or only cortical bone is available. In these cases, current fixation technologies provide less than optimal long-term fixation.
Furthermore, currently available devices which are intended for fixation into cortical (shaft) bone require manual impaction of the device to produce pressure between the device and the host bone, which is challenging to reliably reproduce and thus introduces the potential for surgical error. Other devices use a spring-loaded mechanism to produce compression between metal and only the leading edge of the bone. Thus, the osseointegration surface is limited to a small area and so patients are prohibited from bearing weight for many weeks, and even then, the risk of early failure remains high.
This invention is intended to take advantage of the natural tendency of bone to grow into porous metallic surfaces and develop a durable attachment via “osseointegration”. This occurs when bone progenitor cells migrate into the metallic pores and form bone within and about the porous structure. This process is well known to allow for durable fixation of metal implants onto bone. Within the scope of the present invention, in each of the below embodiments, the porous and non-porous portions of the device may be coated with proteins from synthetic or animal source such as antibiotics, or include other coatings or radioactive materials to augment the therapeutic options of the invention.